The extant literature reporting Alzheimer's disease and related dementias (ADRD)-attributable health care costs in the United States is based primarily on claims data from Medicare fee-for-service (FFS) beneficiaries, thereby leading to an incomplete understanding of current and future costs of ADRD for Medicare beneficiaries enrolled in Medicare Advantage (MA) plans. This is because there are critical differences between Medicare FFS and MA plans in terms of demographics and provision of care service. First, while MA beneficiaries have traditionally been younger and in relatively better health than Medicare FFS beneficiaries, this might not be true for Medicare beneficiaries with ADRD. Our recent work from this grant finds that Medicare beneficiaries with ADRD are actually more likely to switch to MA plans after diagnosis between 2007-2011 (Park et al. 2018). Second, while MA plans must cover the same basic services as Medicare FFS, they often provide additional services that Medicare FFS does not cover. The different service mix may result in different costs of care for Medicare beneficiaries with ADRD, as has been demonstrated in previous research for patients with cancer insured through Medicare FFS compared with those in MA plans.